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Power supply vs. Firewire [message #87078] Fri, 12 April 2019 11:40 Go to next message
shadow is currently offline  shadow
Messages: 10
Registered: May 2018
Junior Member
I have been using my ULN2 with a 2010 MacBook Pro supplying the power via Firewire for a few years now and I am very happy with it.

The other day I was talking to a friend who works in the audio electronics field and he said the pre's are excellent but they might be a bit clamped down, not at their full capability by feeding power to the unit via Firewire as opposed to using a directly power supply.

Is there any truth in this?

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Re: Power supply vs. Firewire [message #87093 is a reply to message #87078] Tue, 30 April 2019 02:28 Go to previous messageGo to next message
shadow is currently offline  shadow
Messages: 10
Registered: May 2018
Junior Member
errrr... what?

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Re: Power supply vs. Firewire [message #87094 is a reply to message #87093] Tue, 30 April 2019 02:47 Go to previous messageGo to next message
bj is currently offline  bj
Messages: 638
Registered: July 2011
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Sorry, for the delay in responding to this; the ULN2 internally uses a switch mode power supply and the 2010 MacBook Pro provides enough power to power the unit. Using the external supply won't really have much of an impact; in particular it will not change the internal voltage rails in any way. I'm not sure what your friend means by "bit clamped down", but I don't think it applies to the ULN-2 design.

Now, as with all things audio, subtle changes can have an audible impact. So you could audition the ULN-2 using the external supply and see if you like it better. But there is certainly nothing to be concerned about. The ULN-2 was designed to be bus powered over firewire; as long as the device supply power has the ability to provide enough current, it works as designed. If the device doesn't, then the ULN-2 won't boot or stay booted. Unfortunately newer versions of the MacBook Pro reduced the output current capability via Firewire and newer MacBook Pros are not able to reliably power the 2882 or ULN-2.

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Re: Power supply vs. Firewire [message #87095 is a reply to message #87094] Tue, 30 April 2019 02:48 Go to previous message
shadow is currently offline  shadow
Messages: 10
Registered: May 2018
Junior Member
Thanks bj

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